Overview
The UC3845NG is a high-performance fixed frequency current mode controller produced by Onsemi. It is specifically designed for off-line and DC-to-DC converter applications, offering a cost-effective solution with minimal external components. This integrated circuit features an oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output ideal for driving power MOSFETs. The UC3845NG is tailored for lower voltage applications, with undervoltage lockout (UVLO) thresholds of 8.5 V (on) and 7.6 V (off).
Key Specifications
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Supply Voltage | VCC | 30 | V |
| Output Current, Source or Sink | IO | ±1.0 | A |
| Analog Inputs (Pin 2, 3) | V(ANA) | -0.3 to 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | 10 | mA |
| Power Dissipation at TA≤25°C (8DIP) | PD | 1200 | mW |
| Power Dissipation at TA≤25°C (8SOP) | PD | 460 | mW |
| Power Dissipation at TA≤25°C (14SOP) | PD | 680 | mW |
| Storage Temperature Range | TSTG | -65 ~ +150 | °C |
| Oscillation Frequency | f | 47 to 57 | kHz |
| Reference Output Voltage | VREF | 4.90 to 5.10 | V |
Key Features
- Current Mode Operation to 500 kHz Output Switching Frequency
- Output Deadtime Adjustable from 50% to 70%
- Automatic Feed Forward Compensation
- Latching PWM for Cycle-By-Cycle Current Limiting
- Internally Trimmed Reference with Undervoltage Lockout
- High Current Totem Pole Output
- Input Undervoltage Lockout with Hysteresis
- Low Startup and Operating Current
- Direct Interface with ON Semiconductor SENSEFET Products
- Pb-Free Packages are Available
Applications
The UC3845NG is designed for use in off-line and DC-to-DC converter applications. It is particularly suited for lower voltage DC-to-DC converter applications due to its UVLO thresholds of 8.5 V (on) and 7.6 V (off). This controller is ideal for applications requiring high performance, minimal external components, and robust protective features such as cycle-by-cycle current limiting and undervoltage lockouts.
Q & A
- What is the primary application of the UC3845NG?
The UC3845NG is primarily used in off-line and DC-to-DC converter applications, especially in lower voltage DC-to-DC converters.
- What are the UVLO thresholds for the UC3845NG?
The UVLO thresholds for the UC3845NG are 8.5 V (on) and 7.6 V (off).
- What is the maximum output current of the UC3845NG?
The maximum output current of the UC3845NG is ±1.0 A.
- What is the typical oscillation frequency of the UC3845NG?
The typical oscillation frequency of the UC3845NG is between 47 kHz and 57 kHz.
- Does the UC3845NG have built-in protective features?
- What is the purpose of the separate power and ground pins in the SOIC-14 package?
The separate power and ground pins in the SOIC-14 package help reduce the effects of switching transient noise on the control circuitry.
- Can the UC3845NG be used with power MOSFETs?
- What is the storage temperature range for the UC3845NG?
The storage temperature range for the UC3845NG is -65°C to +150°C.
- Is the UC3845NG available in Pb-free packages?
- How is the oscillator frequency programmed in the UC3845NG?
The oscillator frequency is programmed by the values selected for the timing components RT and CT.
